The most basic explanation of Pi is that it is the ratio of the circumference to the diameter for a circle. That seems simple enough, but it turns out that Pi is an irrational number - so you can't ...

Originally defined as the ratio between the circumference of a circle and its diameter, pi — written as the Greek letter π — ...

14 March is celebrated by some as the most exciting day in mathematics – when the date lines up in the numbers of the famous constant, Pi or π. But some people would rather it isn’t celebrated at all.